1. Field of the Invention
The present invention relates to a plastic packaging structure, and more particularly, to a packaging shell and a power module having the same.
2. Description of the Prior Art
High power efficiency and high power density are industrial basic demands on power converters; wherein, high power efficiency implies energy conservation, carbon reduction, environment protection, and low operation cost, and high power density means small volume, light weight, low transportation cost, less space occupation, and low built cost.
Therefore, improving the space utilization inside the power converter is one of key factors to make the power converter achieve high power density and high power efficiency. Besides, semiconductor device is also an important factor for improving the space utilization inside the power converter, and the commonly used way is to dispose a plurality of semiconductor devices on a packaging shell for constructing an integrated power module (IPM).
There are several kinds of packaging technologies for the power module, such as metal packaging, ceramic packaging, plastic packaging, etc. Please refer to FIG. 1, which illustrate a conventional plastic packaging structure. As shown in FIG. 1, a power device 5′ is electrically/thermally/mechanically connected with the circuit layer of a substrate 9′ such as the DCB (Direct Copper Bonded), the IMS (Insulated Metal Substrate) and the PCB (Printed Circuit Board) through bonding materials such as solder, sintering paste, and silver paste.
In which, the electrodes formed on the top surface of the power device 5′ are connected to the substrate 9′ via a plurality of aluminum bonding wires 3′, and the power device 5′ is protected by a silicone gel 7′ injected into the shell 1′ of the power module. Moreover, a plurality of terminals 4′ are assembled on the substrate 9′ through bonding materials such as solder for electrically connecting a system circuit board. When assembling the power module, the top surface of the substrate 9′ is assembled to the shell 1′ using a sealing adhesive 10′, and the bottom surface of the substrate 9′ is assembled onto a heat sink 8′ through a thermal conductive grease 6′, and then a plurality of screw bolts 2′ are disposed on the assemble hole set in outer side of shell 1′ for tightly fixing the shell 1′ on the heat sink 8′. By such locking setup, the compressional force applied to the shell 1′ by the screw bolts 2′ would transform to a compressional force on the substrate 9′, such that the substrate 9′ would be compressed on the heat sink 8′ tightly and tightening the heat-conducting thermal silicone grease 6′. So that, by this way, the power loss generated by devices on the substrate 9′ may be highly efficiently transferred to the heat sink 8′ through the thermal conductive grease 6′, and achieve heat dispassion effect with the packaging.
Thus, through above descriptions, it can be informed that the prior technique is firstly screw the shell 1′ to the system circuit board (not shown in FIG. 1), and a compressional force is applied to the shell 1′ by the screw bolts 2′ for pressing the substrate 9′. By such locking manner, the compressional force applied to the shell 1′ by the screw bolts 2′ would transform to a compressional force to the substrate 9′, such that the substrate 9′ would be compressed to the heat sink 8′ tightly by pressing and tightening the heat-conducting thermal silicone grease 6′. So, good heat dispassion can be facilitated with the packaging. However, for the fragile substrate 9′, such as DCB (Direct Copper Bonded), a crack may happen when the shell 1′ is installed by screwing and locking because the fragile substrate 9′ cannot afford the stress applied thereof. Accordingly, the conventional plastic packaging technology is necessary to be further improved.